Exhaust purification apparatus and method for internal combustion engines

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(11)

EP 0 894 962 A3

(12)	EUROPEAN PATENT APPLICATION

(88)	Date of publication A3:
	09.08.2000 Bulletin 2000/32

(43)	Date of publication A2:
	03.02.1999 Bulletin 1999/05

(21)	Application number: 98114006.4

(22)	Date of filing: 27.07.1998

(51)	International Patent Classification (IPC)⁷: F02D 41/14, F02D 21/08, F02D 41/30, F02D 41/04

(84)	Designated Contracting States:
	AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE
	Designated Extension States:
	AL LT LV MK RO SI

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Priority:

28.07.1997 JP 20151297

(71)	Applicant: TOYOTA JIDOSHA KABUSHIKI KAISHA
	Aichi-ken (JP)

(72)	Inventor:
	Mashiki, Zenichiro Toyota-shi, Aichi-ken (JP)

(74)	Representative: Leson, Thomas Johannes Alois, Dipl.-Ing. et al
	Patentanwälte Tiedtke-Bühling-Kinne & Partner, Bavariaring 4 80336 München 80336 München (DE)

(54)	Exhaust purification apparatus and method for internal combustion engines

(57) An exhaust purification apparatus for reducing nitrogen oxides in the exhaust gas emitted from an exhaust passage (14) of an internal combustion engine (1). The catalyst (56) is located in the exhaust passage (14). The catalyst (56) stores nitrogen oxides when the air fuel ratio of air-fuel mixture supplied to the combustion chamber (5) is lean and reduces and emits the stored nitrogen oxides when the air-fuel ratio is rich. An ECU (30) controls the air-fuel ratio of the air-fuel mixture to be rich when the nitrogen oxides stored in the catalyst (56) is reduced and emitted. The ECU (30) judges whether the engine operation is stable. The ECU (30) permits use of the rich spike controll only when the engine operation is stable.

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